Depends on the genre.
but...
1940s: Frank Sinatra, Glenn Miller, Ella Fitzgerald, Billie Holliday, Patsy Cline
1950s: Elvis Pressly or again Frank Sinatra, Tony Bennet. Buddy Holly deserves a mention.
1960s: The Beatles, with Bob Dylan in a distant second. Beach Boys for classic '60s pop. The Supremes or Temptations for MoTown. Johnny Cash should be added here too. Jimi Hendrix and the Stones.
1970s: Led Zeppelin or Elton John sound about right, though Don McClean and Billy Joel wrote two of the definitive songs of the decade. Bruce Springsteen was also big. The Jackson 5 for Motown. The BeeGees if you want to be cynical, which I do.
1980s: What genre? Michael Jackson, Madonna, Queen if you want to be kind to the rock scene or Guns 'N Roses or Bon Jovi if you want to be cruel as well as Run-DMC from the rap side.
1990s: Nirvana easily, followed by an assortment of big genre pieces like Tupac, Notorious, NWA and Eminem. For more rock see perhaps Green Day, Red Hot Chili Peppers and Rage Against the Machine and for more of a straight pop sound Madonna, MC Hammer, Britney Spears, Backstreet Boys, N'Sync were the ugliest images and maybe if you just focus on Matchbox 20, Third Eye Blind, Hootie and the Blowfish, Jewel, Goo Goo Dolls and other '90s college rock it might seem okay.
2000s: Not sure yet. I hope Lady Gaga never makes the list. Eminem, Jay-Z and Beyoncé are there as is probably Outkast and Kanye West. You really are seeing the recession of rock from popular music in this decade. Rock wise? ****. For straight pop Kelly Clarkson, maybe Pink and Avril Levigne spring to mind. I'd like to say people will think back to good music from this decade, but I'm drawing a blank (American Idiot?). Most was very monotone sounding and got good radio play like Gavin DeGraw, but no one is going to remember that crap.
